Deep-Sea Yeti Crab Farms Food on Its Arms

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Deep-Sea Yeti Crab Farms Food on Its Arms

By Mark Brown, Wired UK

A thousand feet below the surface of the Pacific Ocean, a yeti crab "farms" a colony of bacteria on its claws. To help them grow, it waves its pincers over methane and sulfide vents, fertilizing the bacteria and making them good enough to eat.

The crab is a relatively new species, called Kiwa puravida, and was first discovered in 2006. Biologists from Oregon State University describe the crustacean's smart farming behavior in the journal PLoS One.

"We watched the crabs wave their claws back and forth in fluid from a methane seep, and rather than trying to capture bacteria, it appeared that they were providing food to the bacteria already growing on their claws," said lead author of the study, Andrew Thurber, in a press release.

The sun's light can't reach this far down into the ocean, so vent and seep animals have to harness chemical energy released from the seafloor. These specialist bacteria are found on deep sea crabs, shrimp and barnacles.

"But we hadn't before seen that kind of 'farming' behavior in which the host waves its symbionts in seep fluid," says Thurber in the release. "We don't know for certain whether hydrogen sulfide alone fuels [the bacteria], but we suspect it may use both hydrogen sulfide and methane released from the seafloor to exist so far from the sun."

The crabs – part of the yeti family (not that yeti), which wasn't discovered until 2005 – also have a specially adapted appendage to scrape the bacteria off their bodies and bring it to their mouths.